Conventional heat sealing machines are of two general types. The two types include a clam shell type and a swing away type. Both machines include upper and lower platens which are movable relative to one another and thereby registerable in a closed position. A heat source is included in one of the platens. Thermally bonding indicia such as letters, numbers and identifying logos are applied to a fabric such as a T-shirt, sweatshirt or other garment by placing the indicia on the fabric between the platens, applying pressure to force the platens toward one another and at the same time applying heat sufficient to cause the thermally bonding indicia to stick to the fabric. After an appropriate time interval, the platens are separated and the fabric with indicia attached is removed.
These two types of machines can further be categorized as manual, semi-automatic and automatic machines. All machines require an operator. The manual machines require the operator to control the pressure between the platens, the temperature and the time during which the pressure and temperature is applied to the indicia and fabric. Semi-automatic machines require the platens to be registered manually but release the platens automatically after the timing cycle. Automatic machines require compressed air or a motor to supply the force required to move the platens into a registration position and apply pressure and subsequently separate the platens after the timing cycle. Pressure between the platens during registration in these machines is a function of the force of the operator or other mechanical means used to accomplish registration. No manually operated or semi-automatic machines are known which include a means to control or regulate the pressure between the platens. This inability to control the pressure between the platens doesn't allow the operator to know that the pressure being applied is correct and results in inconsistent duplication when each of the same sets of letters and fabrics must be set up for bonding for each application. When incorrect pressure is applied, as often it is, a less than optimal bond between the indicia and fabric results.
The time during which the platens are registered is equally important as is the pressure applied and also the heat to insure a good bond of the letters to the garment. On both the manual and semi-automatic machine, the timing cycle is initiated by the operator and most often the timer is a clock or wristwatch although other types of timers have been employed. The inconsistency of having a human operator initiate the timing cycle gives rise to having different periods of application of pressure between the platens to similar letters and fabrics which leads to poor bonding.
Furthermore, no manually operated or semi-automatic machines are known which simultaneously control pressure, time and temperature. All of these variables are dependent upon one another yet no heat sealing machines simultaneously control these variables to provide an efficient application operation.